Extraction of Algal ATP and Interpretation of Measurements

Abstract

We compared ATP samples collected by direct injection with those collected by filtration from exponential and P-limited algal cultures, and from summer populations of several lakes. The direct injection method yielded higher amounts of measurable ATP than did filtration on 2.5- and 4.5-cm diameter membrane filters. ATP lost to the filtrate was negligible. Variation in ATP content with increasing nutrient deficiency was measured on six cultures. ATP/C decreased with N deficiency and to a greater degree with P deficiency. Large changes of ATP/C usually occurred with little change in viability of the cells. Short-term (1 h) nutrient enrichments generally did not change the ATP/C ratio. Phosphorus deficiency tended to increase the chlorophyll/ATP ratio and N deficiency to decrease it. We found that the short- and long-term effects of alkaline phosphatase on ATP extracts from P-sufficient and P-deficient Scenedesmus quadricauda were negligible. There appeared to be little effect on frozen ATP samples stored up to 60 d. Any short-term effects were similarly negligible, since temperature and the addition of P did not affect the rate of ATP loss. The use of 0.33 mol H3PO4∙L−1 as an extractant proved to be completely unreliable.